MICROBIAL PRODUCTION OF LIPOPEPTIDES AS BIOSURFACTANTS FOR VARIED APPLICATIONS

摘要

Biosurfactants have excellent surface active properties and strong antimicrobial activities making them suitable candidates for applications in varied industries such as personal care, foods, animal feeds and agriculture. However, the high production cost severely limits their industrial applications. Hence, screening high titre of biosurfactant-producing strains and improving them via whole cell mutagenesis or metabolic engineering are crucial to make them commercially attractive. Bacillus subtilis CX1-2 was isolated, which is able to produce surfactin at 1.2 g/L. The surfactant production was improved by 30% by whole cell mutagenesis induced by the atmospheric room temperature plasma (ARTP). Anti-microbial studies showed that Bacillus subtilis CX 1-2 has inhibitory activity against Rhizobium radiobacter, a pathogen that causes food spoilage in a large number of products. The em unification study indicated that the biosurfactant produced by Bacillus subtilis CX 1-2 has much better performance than commercial emulsifiers used in foods such as phosphatidylcholine from egg yolk. Bacillus subtilis 22.2 was isolated, which produces surfactin as the major product with small amount of fengycin. Preliminary experiments showed that this strain is able to tolerate 40 g/L of sodium surfactin. Whole cell mutagenesis and metabolic engineering of the isolates based on CRISPR/Cas9 are ongoing to improve the biosurfactant production.